The Strangles Vaccine Gap Buyers Should Know

Early October is when a meaningful share of the American hunter/jumper market unfolds in Europe, out of sight of most of the circuit back home. Agents and buyers are moving through sales barns in the Netherlands, Belgium, and Germany, trying young horses that will ship west before the indoor circuit gives way to Wellington and Thermal. This year, more of them than usual are shopping into an outbreak most have never had reason to think about.

Strangles, the contagious bacterial infection caused by Streptococcus equi, is not new and not exotic. It is one of the oldest diagnoses in equine medicine, which is exactly why it gets filed under backyard barns and boarding facilities rather than the sport horse pipeline. The United Kingdom's 2026 numbers argue otherwise. Surveillance of Equine Strangles data, reported independently by both Horse & Hound and Vet Times, puts the count at 260 diagnosed cases between January and May, climbing to 274 by June 23 -- already more than half of the 479 cases recorded across all of 2025. The spread covers Northern Ireland, Scotland, Wales, and most of England. Horse & Hound also reported that just over a third of those 274 cases were in horses showing clinical signs, which means close to two-thirds were identified in horses that were not obviously sick.

What the Carrier State Actually Hides

That ratio is the real story, more than the raw count. Strangles earned its name from the swollen lymph nodes that can compress a horse's airway, but the more dangerous version of the disease produces no abscess, no fever on a health certificate, and no reason for a buyer, a quarantine officer, or a show steward to look twice. A horse can recover from strangles, swab clean at the wrong moment, and still carry Streptococcus equi in its guttural pouches for months or years, shedding it intermittently to every horse that shares a water trough or a trailer. Endoscopic examination of the guttural pouches, not a glance and a temperature log, is the only reliable way to find that horse. Almost nothing in standard import or show-entry paperwork asks for it.

The Vaccine Europe Already Has

Europe has a tool the United States still does not. Strangvac, built from eight recombinant proteins rather than live or killed bacteria, is licensed in the UK, the EU, Norway, Iceland, and Liechtenstein, and is now distributed in sixteen European countries through an agreement between its Swedish manufacturer, Intervacc AB, and Dechra. Its design solves a genuine problem: because the vaccine omits the SeM protein that most commercial blood tests use to detect natural exposure, a vaccinated horse does not read as falsely infected on the assay a vet would reach for during an outbreak investigation. A 2023 genomic study in the Equine Veterinary Journal, examining 759 Streptococcus equi isolates collected from nineteen countries between 1955 and 2018, found three of the vaccine's core antigens genetically identical across virtually the entire collection -- a strong argument that its coverage does not depend on which strain happens to be circulating in a given region.

The Label's Fine Print

Here is where the case gets less tidy. The vaccine's European product label recommends repeating the full two-dose primary course every two months in horses at high risk, which reads less like a maintenance schedule than an admission that protection barely lasts long enough to matter. A 2025 review in Equine Veterinary Education, led by David Rendle, past president of the British Equine Veterinary Association, argues the two-month figure reflects how long the manufacturer's challenge studies ran, not proof that protection actually fades on that timeline. Rendle and his co-authors recommend boosters every six to twelve months under ordinary risk, tightening to every three months only where the disease is confirmed to be circulating. Intervacc appears to agree with its own critics: in July 2026 the company filed a variation with the European Medicines Agency seeking to extend the labeled duration of immunity to twelve months, citing a new peer-reviewed study showing antibody levels remaining protective for a year. The filing is still under review. Until it clears, a European vet recommending this vaccine on anything longer than a two-month cycle is reading past the label, not from it.

The Vaccine America Doesn't Have Yet

In the United States, there is no label to read past, because there is no vaccine. Intervacc filed for a U.S. distribution permit with the USDA's Center for Veterinary Biologics in February 2022. Safety trials in American horses did not begin until December 15, 2025, covering roughly six hundred horses across four states under USDA protocol, with efficacy studies not slated to start until the second half of this year. However the European duration-of-immunity question resolves, it will have resolved years before an American buyer has the option to vaccinate against this disease at all.

None of this is a European problem borrowed for a slow news week. The Equine Disease Communication Center logged confirmed strangles cases in the United States this year as well, including a Florida carriage-horse facility in January and quarantines across two Wisconsin counties, with a cluster just over the border in British Columbia in March. The American show circuit is not immune to this disease. It is simply not counting it the way the UK now does, and it will not have a vaccine to reach for regardless of how carefully it counts.

The sport has spent much of this year writing rules for blood on a horse's side and warnings for noseband tension -- the kind of visible welfare failure that photographs well and votes well at a General Assembly. A bacterium that sits unnoticed in a guttural pouch for months does not photograph, does not trigger an elimination, and is not on any federation's agenda. For the buyer flying to a European sales barn this month, that absence of a rule is the only rule currently in effect.